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Old 06-01-2007, 05:11 PM
Bolt Bolt is offline
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Join Date: Oct 2004
Location: Texas
Posts: 1,267

Alright, lots of action here, there's always somebody who knows something about everything around these parts. I am also starting to think that a PLC is going to make life easier in this application.

The gate currently moves by an air motor, which grabs a roller conveyor chain (fixed ends) and moves along it. The controls are air over air, no electricity what so ever. The gate doesn't need to be controlled by anything new, the way it is is fine. So it is entirely possible and quite likely that the gate moves when the power is interupted, but our power outages rarely last more than 2 seconds, as the standby diesel generator kicks in instantly. Also, it's not supper critical that it work 100% of the time, as long as it would reset when the gate goes all the way forward again.

I am trying to relay some coils for solenoid valves. I think a PLC would work well here, that way no relays are needed, just hook them up to the outputs.

The gate has a travel of 120 feet, not 200 like mentioned earlier.

Once the gate, moving from 120 feet away towards 0, gets past 60, the back valve needs to shut off. Once the gate clears 50, another one shuts off. Once it's past 40, another valve turns off, so the back 3 are off, the front 3 are still on. 30 feet or closer the front 2 are on, the back 4 are off. 20 feet or closer, just 1 is on, the back 5 are off. The front one never turns off.

Overall, these valves need to be controlled as a group, depending on the gate's position, by a timer, something like 1 minute on, 9 off. The rest of the 9 minutes another external contactor need to be triggered. These minutes need to be fairly tweakable, the distance stuff isn't going to need to be changed too often.

Now, what do I need in a PLC and a pot to do this? What else do I need.

The valves are 24V, not sure if it's AC or DC right now, the external contactor can be 120VAC, and then the pot needs a power source.

Now that everybody is thoroughly confused, lets keep going with the discussion!
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Last edited by Bolt; 06-01-2007 at 05:20 PM.
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